This invention relates to a vehicle dynamic characteristic control apparatus for use with an automotive vehicle.
For example, Japanese Patent Kokai No. 61-67665 discloses a vehicle steering control apparatus for controlling a vehicle dynamic characteristic based upon various vehicle operating conditions. The apparatus includes a control unit for calculating a target yaw rate from a vehicle model specifying the target yaw rate as a function of vehicle speed and vehicle steering condition. The control unit controls the rear-wheel steering angle to achieve the target yaw rate.
During vehicle braking, however, the tire frictional forces serve to brake the vehicle and the front- and rear-wheel cornering forces change from those produced in the absence of vehicle braking. As a result, the transient and steady characteristics of the produced yaw rate are different in the presence of vehicle braking than in the absence of vehicle braking. For this reason, it is impossible, during vehicle braking, to bring the produced yaw rate into coincidence with the target yaw rate value merely by controlling the rear-wheel steering angle.